/*
 * Copyright 2012 The Netty Project
 *
 * The Netty Project licenses this file to you under the Apache License,
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */
package io.netty.handler.codec.socksx.v4;

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.DecoderException;
import io.netty.handler.codec.DecoderResult;
import io.netty.handler.codec.ReplayingDecoder;
import io.netty.handler.codec.socksx.v4.Socks4ClientDecoder.State;
import io.netty.util.NetUtil;

import java.util.List;

/**
 * Decodes a single {@link Socks4CommandResponse} from the inbound
 * {@link ByteBuf}s. On successful decode, this decoder will forward the
 * received data to the next handler, so that other handler can remove this
 * decoder later. On failed decode, this decoder will discard the received data,
 * so that other handler closes the connection later.
 */
public class Socks4ClientDecoder extends ReplayingDecoder<State>
{

    enum State {
        START, SUCCESS, FAILURE
    }

    public Socks4ClientDecoder()
    {
        super(State.START);
        setSingleDecode(true);
    }

    @Override
    protected void decode(ChannelHandlerContext ctx, ByteBuf in,
            List<Object> out) throws Exception
    {
        try
        {
            switch (state())
            {
                case START:
                {
                    final int version = in.readUnsignedByte();
                    if (version != 0)
                    {
                        throw new DecoderException("unsupported reply version: "
                                + version + " (expected: 0)");
                    }

                    final Socks4CommandStatus status = Socks4CommandStatus
                            .valueOf(in.readByte());
                    final int dstPort = in.readUnsignedShort();
                    final String dstAddr = NetUtil.intToIpAddress(in.readInt());

                    out.add(new DefaultSocks4CommandResponse(status, dstAddr,
                            dstPort));
                    checkpoint(State.SUCCESS);
                }
                case SUCCESS:
                {
                    int readableBytes = actualReadableBytes();
                    if (readableBytes > 0)
                    {
                        out.add(in.readRetainedSlice(readableBytes));
                    }
                    break;
                }
                case FAILURE:
                {
                    in.skipBytes(actualReadableBytes());
                    break;
                }
            }
        }
        catch (Exception e)
        {
            fail(out, e);
        }
    }

    private void fail(List<Object> out, Throwable cause)
    {
        if (!(cause instanceof DecoderException))
        {
            cause = new DecoderException(cause);
        }

        Socks4CommandResponse m = new DefaultSocks4CommandResponse(
                Socks4CommandStatus.REJECTED_OR_FAILED);
        m.setDecoderResult(DecoderResult.failure(cause));
        out.add(m);

        checkpoint(State.FAILURE);
    }
}
